1. Field of the Invention
The present invention relates to a micro cooling fan, and more particularly to a micro cooling fan in which a driving circuit is disposed on an outer surface of a housing to achieve an integral structure of the housing and the driving circuit of a micro fan motor.
2. Related Art
In recent years, an electronic device is disposed with a variety of electronic elements, such as a central processing unit and a power supply. Since the electronic elements will generate a lot of heat when the electronic device is running, a cooling fan needs to be mounted to remove heat, so as to prevent the life of the electronic elements from being shortened due to an excessively high temperature of the electronic elements.
A direct current fan motor structure which is disclosed uses a control circuit device to control the electromagnetic effect of a stator device such that a rotor device is rotated by an electromagnetic repulsive force of the stator device. In the stator device, a hollow coil set is sleeved on a ring magnet of a magnetically conductive sleeve, and an upper silicon-steel sheet and a lower silicon-steel sheet of a silicon-steel sheet set are disposed on a top edge and a bottom edge of the magnetically conductive sleeve and the ring magnet respectively. The main characteristic lies in that a periphery of each silicon-steel sheet is provided with four symmetric protruding portions. Wherein, the four protruding portions of the upper silicon-steel sheet and the four protruding portions of the lower silicon-steel sheet are alternately arranged, and one side edge of each protruding portion is slightly larger than the other side edge, thereby forming an asymmetric design. Since the control circuit device is located below the stator and in an axial direction of the fan, poor heat dissipation is caused, resulting in that the life of electronic elements on the control circuit device is reduced. Moreover, since the area of the electronic elements disposed on the control circuit device is limited by a maximum outer diameter of the motor, it is difficult to arrange and dispose the electronic elements.
A cooling fan which is disclosed includes a frame and a fan wheel. The frame has an air-intake surface, an air-outlet surface, an inner annular wall, an axial air channel, and a bearing portion. The bearing portion is formed on at least a portion of a frame edge, and includes a first side wall, a second side wall, and a loading space. The first side wall is formed by at least a portion of the inner annular wall, and the second side wall is spaced apart from the first side wall. The loading space is formed between the first side wall and the second side wall, and is used to bear a driving circuit board. Since the driving circuit is placed in the loading space of the inner annular wall, the air volume of the cooling fan is increased, and the cooling problem of the driving circuit is solved. However, in the manufacturing process of the above cooling fan, the loading space needs to be disposed in the inner annular wall of the frame to place the driving circuit. The manufacturing process of the frame is complex, and a consideration has to be given to the cooling of the driving circuit.
In addition, when the cooling fan is used in an Internet terminal, the cooling fan needs to be miniaturized. However, in the miniaturization process of the cooling fan, a three-phase motor structure needs to be used so as to lower the power consumption of the cooling fan, and since the three-phase motor requires a larger disposition space than a single-phase motor, a problem regarding whether a micro cooling fan has an extra space for disposing the driving circuit is imposed.